I'd go the serviced apartment first for a look around. HK has so many different areas to live, its well worth spending some time in all of them before you decide to settle down in one of them.
Any particular reason you're looking at Tai Tam? As an expat it would be an interesting place to live - unless you have specific reasons for living there I'd rather live somewhere else.
Its a nice enough area, but:
** its mainly all HUGE apartment blocks. not much else in the way of bars or restaurants in that area (even foodbyweb doesn't deliver much out that way). I went there once for a look around and got kind of depressed. So many apartments, so few facilities, all packed into such a small area.
** not that there's anything wrong with it, but its very local - you wont' find too many expats out that way.
** good 40 minutes to Central, and either way you have to change trains. Same goes to TST, which is still half an hour away. This is a loooong travel time by HK standards.
On the up side, its close to Sai Kung and the New Territories countryside. Kowloon Tong / Pacific Place aren't too far away either for shopping.
Most places offer either one or two year lease. Even with two year lease you're really only tied in for one year. It has a break clause after that so you can leave with two months notice if you wish.
My advice would be to go into a serviced apartment first and have a look around. Go out to Tai Tam a few times, including trying to get there in the afternoon peak, so you can work out if its really for you.